The significance of the above studies lies firstly in a basic understanding of non-specific cell mediated suppression as a phenomenon both in vivo and in vitro. In addition, data generated over the past year of funding has led to the hypothesis that lymphoblasts can suppress and that lymphoblast mediated suppression under these circumstances could be operative in vivo as an autoregulatory phenomenon at the local level within the confines of a lymph node or spleen. Lymphoblasts could autoregulate the degree of a response by achieving a critical blast to responder cell ratio within the lymph node and thus, nonspecifically shut off responsiveness to an antigen. Such a type of regulation would be transient, nonpermanent and not antigen specific and would merely reflect the ratio of responsive small cells to large responding blast cells after an antigen challenge in vivo. A third and probably most significant aspect of this research deals with the potential role suppressor cells play in vivo in allograft responses. The analogy, of course, is with transplantation and biologic methods of immunosuppression, this being adoptive transfer of in vitro generated suppressor cells. This could have great significance in the field of clinical organ transplantation if such a method could be made specific and provide long lasting immunosuppressive effect.